JPS60218579A - Method and device for liquefying gas - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides gas at a first pressure greater than atmospheric pressure supplied by a gas supply device to a cooling device, and then brings the produced liquid to a second pressure equal to or lower than said first pressure. The present invention relates to a method of liquefying the gas by doing so. Furthermore, the present invention relates to a liquefaction apparatus for implementing the method 1j;1.

Known methods of the type mentioned at the outset (presented at the GASTE C11 conference held in Houston, USA in 1979 [LNG/Lr' by pressure swing adsorption]
Nitrogen for LNG /L
PG 5hips by pressure swing
adsorption) J.

(as disclosed in the publication by Feibusch et al.), nitrogen gas is condensed in a cooling device and collected in liquid form in a storage vessel. Nitrogen that evaporates within the storage vessel due to refrigeration leakage is returned to the cooling system where it is recondensed to maintain the level of liquid nitrogen within the storage vessel. If a gas separation device is not available, liquid nitrogen is fed from a storage container to an evaporator and then delivered in gaseous form to the user. Of course, it is also possible to remove liquid nitrogen directly from the storage container, but known devices are not primarily designed for this purpose.

A disadvantage of the known method is that, after the liquid nitrogen has been removed from the storage container, nitrogen gas is generated due to cold leakage and/or pressure drop along the path between the storage container and the user, and the user cannot remove the liquid from the storage container. Nitrogen gas is of little value to the user if nitrogen is desired. Moreover, the nitrogen gas produced indicates that a certain amount of refrigeration is not being utilized. Furthermore, the location of the cooling device is limited to the top of the storage vessel to prevent the cooling device from filling up with already condensed return liquid.

The object of the invention is to provide a method as described at the outset, which does not have the above-mentioned disadvantages.

Another object of the present invention is to provide a liquefaction device for carrying out the method of the present invention.

The method according to the invention comprises supplying the gas flowing out of the gas supply device to the cooling device after cooling it through a first gas/gas heat exchanger, and subsequently producing a saturated liquid and a liquid by condensation in the cooling device. directing the wet vapor to a liquid separator, placing the saturated liquid discharged from the liquid separator and the wet vapor produced by expansion after the liquid separator into the liquid already forming in a thermally insulated storage tank; Second to do
The saturated liquid and the wet vapor are subcooled and condensed/subcooled in the second heat exchanger, respectively, and the degree of subcooling is controlled by a pressure controller connected to the second heat exchanger. achieving and then adjusting said second pressure between a value corresponding to a maximum value of said second pressure equal to the pressure in said cooling device and a value corresponding to a minimum value of said second pressure equal to the pressure in said reservoir. and evaporate a portion of the liquid present in the thermally insulated storage tank using condensation heat and subcooling heat;
The vapor thus generated is guided to the first heat exchanger to cool the gas supplied by the gas supply device, and the liquid evaporated in the storage tank is transferred to a supply conduit connected downstream of the liquid separator. It is characterized by being replenished by.

The liquefaction device of the present invention supplies gas at a first pressure higher than atmospheric pressure supplied by the gas supply device to the cooling device,
In a gas liquefaction device that then liquefies the gas by bringing the produced liquid to a second pressure equal to or lower than the first pressure, the output I of the gas supply device is connected to a thermally insulated first heat exchanger. coupled, the first heat exchanger, together with a second heat exchanger and a liquid separator, being located within a thermally insulated reservoir and coupled to a cooling device, the cooling device being located outside of the thermally insulating reservoir; A liquid conduit of the cooling device is connected to the liquid separator, the liquid separator having an outlet conduit, the outlet conduit being connected to the second heat exchanger and to a user via a pressure controller. the opening pressure of the pressure controller is independent of the user pressure; and the thermally insulated vessel is provided with a level control f11, the level controller being connected to the outlet conduit of the liquid separator. It is characterized by being connected.

The cryogenic liquid (c
ryogenic 1equid) from a supply device to a user is itself described in U.S. Pat. No. 4,296,610.
Known from the specification. However, the heat of condensation and subcooling released during condensation and subcooling is lost, which can even lead to an increase in the temperature and pressure of the cooling liquid, and there is a need to eliminate such drawbacks.

The invention will now be explained by way of example with reference to the drawings.

The liquefier shown in FIG. 1 comprises a gas supply in the form of a gas separator 12 which comprises two molecular sieves 14 and 16. The liquefier shown in FIG. The gas separation device 12 is of a type known per se, for example X4. F+41 fuel (Fu
el) J, Vol. 60, pp. 817-822 (September 1981 issue). Air is sucked in by a compressor 20 through an artificial conduit 18, and this air is outputted through a conduit 2 at a pressure of, for example, 6.5 kP (kilopascal).
Send it out during 2nd. Outlet conduit 22 is connected to cocks 24 and 26
can be linked to molecular sieves 14 and 16, respectively. The molecular sieves 14 and 16 are further connected by cocks 28, 30 and 32 to an outlet conduit 34 in which a vacuum pump 36 can be arranged. If the compressor 20 has a relatively high delivery pressure, for example 6.5 kP, the vacuum pump 36 can be turned off. Molecular sieves 14 and 16 separate nitrogen gas from oxygen gas. Oxygen gas remains within these sieves and nitrogen gas is pumped into supply conduit 44 via ports 38, 40 and 42.

If the cocks 24, 26, 28, 30, 32, 38. The sieves are cleaner by not blowing the absorbed oxygen out into the atmosphere. So the average pressure is 6.5
A nitrogen gas flow of kP is obtained. Nitrogen gas is supplied through the supply conduit 44
via a thermally insulated storage tank 48 and, in particular, into a gas/gas heat exchanger 50 arranged within this storage tank. Nitrogen gas enters heat exchanger 50 at 1 and leaves heat exchanger 50 at 2. Reference numbers I to IO are also used to explain the thermodynamic procedure of the method according to the invention with respect to FIGS. 4 and 5, where corresponding reference numbers 1 to 10 are used. "I'm here." Nitrogen gas huff in 1,
The degree is 288°. In the heat exchanger 50, 288
Nitrogen gas at 78° is 243″ by cold nitrogen gas at 78°
This cold nitrogen gas is pre-cooled to a temperature of
It enters the heat exchanger at 10 and leaves the heat exchanger at 10. This cold nitrogen gas is then heated to 288°K.

Two concentric pipes are used to transfer cold in the heat exchanger 50, with relatively high temperature nitrogen gas in the inner pipe and relatively low temperature nitrogen gas between the outer and inner pipes. Can pass. The heat exchanger 50 is thermally insulated from the interior of the reservoir 48 by an insulating material 51 (liquid 2), for example polyurethane foam. A method for obtaining cold nitrogen gas for the heat exchanger 50 will be further explained.

The precooled nitrogen gas leaves heat exchanger 50 at a temperature of 243° and is conducted via conduit 52 to cooling device 54 . The cooling device 54 is of a type known per se, for example by J.H., W., L., Keller and C.H., O., Jonkers, "Philips Technical Review".
, Vol. 16, pp. 105-115 (October 1954 issue). This cooling device houses a heat exchanger 56, which allows three
The nitrogen gas entering at a temperature of 243° and a pressure of 6.5 kP condenses. The liquid nitrogen leaves the heat exchanger 56 at 4 at a temperature of 96° and a pressure of 6.5 kP.

The cooling device 54 is connected by a conduit 58 to a liquid separator in the form of a liquid tiger knob 60 located within the thermally insulated reservoir 48 (see also FIG. 3). Liquid nitrogen 62 is collected at the bottom of liquid trap 60. Above this liquid nitrogen is gaseous nitrogen 64, which comes from the refrigeration system 54 and which is transferred to a pressure balance conduit 65 (dashed line) during the start-up phase of the liquefier. 1952 to prevent liquid nitrogen in conduit 58 from returning to cooling device 54. As soon as the liquid nitrogen level 66 reaches a predetermined height, either the valve 68 or the float 67 opens and liquid nitrogen is pumped into the conduit 70. Conduit 70 connects liquid trap 60 to a liquid/liquid gas heat exchanger 72 (second heat exchanger) located within reservoir 48 . Heat exchanger 72 is located in liquid nitrogen 74 at 78°, which is generated during the start-up phase of the liquefaction process. In the heat exchanger 72, the liquid nitrogen at a temperature of 91° entering the heat exchanger at 5 is cooled and subcooled to a temperature of 78°K at 7, respectively. Furthermore, the liquid trap 60
The nitrogen gas generated by the pressure drop due to
and then subcooled along the path indicated by 6-7. A T-branch 76 is arranged downstream of the heat exchanger 72. At this T-junction, conduit 78 connects heat exchanger 72 to pressure controller 80 and supply conduit 82 connects heat exchanger 72 to level controller 84 . The level controller 84 will be further explained.

A pressure regulator 80, shown in detail in FIG. 3 and only diagrammatically for node ii'L in FIG. 2, is arranged in the reservoir 48. The pressure regulator 80 comprises a valve comprising a disc valve element 88 which is secured by a rod 90 to a disc-shaped support 92 . Preferably, the surface of the disc valve element 88 and the surface of the disc-shaped support 92 over which liquid nitrogen flows are equal in area.

Below the opening pressure, the valve element 88 engages an annular valve seat 94 which is secured within the conduit 78 .

A relatively loosely corrugated bellows 96 is secured at one end to the support 92 and at the other end to a sleeve 98, which is secured within the conduit 78. The sleeve 98 has an adjustment screw 1.
A screw thread is provided for adjusting 00. A coil spring 102 is arranged between the adjustment screw 100 and the support body 92. Coil spring 102 is harder than Perot 96.

When valve element 88 is open, conduit 78 communicates with conduit 106 by passage 104 in valve seat 94. Conduit 10
6 is connected to a storage container 108, which has an outlet conduit 110, which is provided with a stopcock 112 for the user. If the prestress of spring 102 is equal to V and the surface areas of support 92 and valve element 88 are equal to 8, the opening pressure p+ is equal to V/A. This term means that the opening pressure 1]+ is independent of the user pressure p2 (second pressure) in the conduit 106 and the storage vessel 10B.

Therefore, by adjusting the prestress (2), the pressure drop due to the liquid trap can be adjusted.

The level controller 84 has a valve 114 (see FIG. 2), which can be opened and closed by a flow eye 16, and the float 116 moves up and down according to the level 11B of liquid nitrogen in the reservoir 48. When valve 114 opens, liquid nitrogen enters conduit 1.
20 and added to the liquid nitrogen 74 in the storage tank 48. During the start-up phase of the liquefier, the cooling device 54 supplies liquid nitrogen to the reservoir 48 until the level 118 reaches the height it would have if the valve 114 were closed. Since the liquid nitrogen and gaseous nitrogen in heat exchanger 72 continually impart heat to liquid nitrogen 74, a portion of liquid nitrogen 74 is continuously vaporized. This evaporated nitrogen at 78° is fed to the gas/gas heat exchanger 50 at 9 and is used to pre-cool the nitrogen gas fed by the gas separation device 12. Heat exchanger 72
The nitrogen in the storage tank 48 that has been evaporated is constantly replenished by the level controller 84. A level controller 84 can also be coupled to conduit 70 downstream of liquid trap 60.

The method of the invention and its possibilities will be explained in more detail with reference to FIGS. 4 and 5. If the prestress ■ is increased in the manner indicated by the sequential numbers 1 to 10 in FIGS. 4 and 5, the opening pressure p+ is
For example, it rises to the levels indicated by 5', 6' and 7'.

The degree of subcooling increases by an amount determined by the length difference between paths 6-7 and 5'-7'.

Therefore, the ratio between subcooling enthalpy Δ110 and condensation enthalpy Δ11c changes, but the sum of subcooling enthalpy and condensation enthalpy ΔH−Δ
H and +Δ remain constant. Therefore, the heat exchanger 72
The total amount of heat imparted to liquid nitrogen 74 in reservoir 48 (paths 8-9) by the liquid nitrogen and gaseous nitrogen in storage tank 48 is always equal and exactly equal to the cooling capacity of heat exchanger 50. The user pressure p2 is p. and pmax, so it can vary by an amount of Δ.

Therefore, as the service pressure p2 increases or decreases, the degree of subcooling of the extracted liquid nitrogen increases or decreases.

If the second pressure or user pressure p2 is lower than the opening pressure p1 and greater than or equal to the pressure in the reservoir p0 (ie p.≦pz<T1+), then
achieved by the user. The subcooling is less than the subcooling ΔI+ achieved by heat exchanger 72. The pressure between the liquid trap 60 and the pressure regulator 80 is in this case constant pl, since the pressure regulator 80 is closed at a pressure higher than pl. The user pressure p2 is less than or equal to pmax and the opening pressure p is greater (i.e. I) I
<I)2≦p188), the subcooling achieved by the user is greater than the subcooling ΔH, achieved by the second heat exchanger 72. The pressure between liquid trap 60 and pressure controller 80 is now p2.

If the user pressure p2 is equal to the opening pressure p1, the subcooling achieved by the user is equal to the subcooling ΔHo achieved by the heat exchanger 72. The pressure between liquid trap 60 and pressure controller 80 is now p
+=pz. In this way, the result is that the user can vary the degree of subcooling and the user pressure as desired. By cook 112,
The user can extract liquid nitrogen. User pressure p
2 can be regulated by providing a vacuum cock 113 and an evaporator 115 with a feed hack to the storage vessel 108 via conduit 117 to bring it to ambient temperature. This is extremely important, since the pressure loss that always occurs on the user side no longer results in the formation of nitrogen gas. The degree of subcooling for the user that can be adapted to this pressure loss is in fact the user pressure p2
and the pressure p in the storage tank 48.

(see Figure 4). If the user requires subcooled liquid nitrogen, the user pressure p2 will be higher than the pressure po in the storage tank 48, so the pressure p. (Symbol 8) is not achieved. Pressure p in reservoir 48. is often equal to atmospheric pressure. pressure controller 80
determines the pressure drop across liquid trap 60 and thus the level of path 5-7 in FIG. The temperature difference is also determined (see Figure 5).

In the example of storage tank 48 shown in FIG. 2, heat exchanger 50 consists of two concentric pipes (not visible in the drawing).

Nitrogen gas from the gas separator 12 enters the heat exchanger 50 at 1 via conduit 44 and passes through conduit 52 (in FIG. 2 conduit 58).
2) leaves the heat exchanger at 2,
Conduit 52 is connected to cooling device 54 .

The cold nitrogen gas evaporated in reservoir 48 enters heat exchanger 50 at 9 and leaves this heat exchanger at 10.

The heat exchanger is carried out according to the countercurrent principle. The nitrogen gas heated in the heat exchanger 50 exits the storage tank 48 and is guided into the surrounding air, so that the atmospheric pressure (0.98 kP) is maintained within the storage tank 48.
) is predominant. If a pressure controller is integrated in the conduit to the ambient air, a pressure greater than atmospheric pressure can be obtained in the reservoir 48. In this case, the pressure in Figure 4 -
In the enthalpy diagram, paths 8-9-10 are located at higher pressure levels. Therefore, in addition to the ratio of condensation enthalpy and subcooling enthalpy along path 5-6-7 (at constant condensation enthalpy), the sum of the two enthalpies and therefore the storage tank 4 available for precooling
The amount of nitrogen evaporated from 8 changes. In this way, the degree of preliminary cooling can be adjusted.

Although the liquefier has been described using nitrogen, other substances such as oxygen, hydrogen, methane, argon, etc. can also be used. For this purpose, it is only necessary to use a gas separation device ff 12 and a cooling device 54 that are compatible with these substances. The gas supply device is not limited to a gas separation device 12 comprising a molecular sieve. Known so-called gas separation columns, which separate gases from each other using their boiling point differences, can also be used. In such cases, after separation, the gas is brought to a pressure greater than atmospheric pressure by means of a compressor to allow optimal utilization of the cooling system. Although the production of refrigeration by the cooling device actually increases at higher pressures of the feed gas (relatively higher condensing temperatures), the power consumption of the cooling device remains unchanged. At relatively high condensation temperatures, the pressure of the working medium, such as helium gas, in the cooling system can be increased, but the load on the cooling system is reduced. By using a pressure greater than normal pressure for the product gas fed to the cooling device, there is no need for further pumping devices. The pressure is supplied by a compressor already present in the gas separation device comprising the molecular sieve.

Alternatively, the gas supplied to conduit 44 can be from a storage container.

A liquid separator in the form of liquid trap 60 performs two functions. First, the saturated liquid from the cooling device 54 is transferred to the cooling device 5.
Separate from the wet steam from 4. Additionally, liquid trap 60 acts as a check valve so that even if reservoir 48 is located at a higher level than cooling device 54, liquid cannot flow back into the cooling device. In fact, instead of a liquid trap, any liquid separator can be used, for example a container containing a saturated liquid and a saturated vapor in thermal equilibrium, and in this case an optical sensor instead of a float can be used. use. The optical sensor controls the liquid separator valve. Such optical sensors can also be used in place of floats in level controllers.

The temperature range temperature from 288 to 78° and 6.5°
Although a pressure range of ~1 kP has been described, the present invention is not limited to this range. The possible operating range is given by the pressure-enthalpy and temperature-enthalpy diagrams of the gas in question.

[Brief explanation of the drawing]

1 is a sectional view of an example of the device of the present invention, FIG. 2 is an enlarged sectional view of a thermally insulated storage tank in the device of FIG. 1, and FIG. 3 is an enlarged sectional view of a pressure controller in the device of FIG. 2. FIG. 4 is a pressure-enthalpy diagram according to the method of the present invention, and FIG. 5 is a pressure-entropy diagram according to the method according to the present invention. ■...Nitrogen gas inlet 2 in heat exchanger 50...Nitrogen gas outlet 3 in heat exchanger 50...Heat exchanger 56
14...liquid nitrogen outlet 5 in the heat exchanger 56...liquid nitrogen gas in the heat exchanger 72
Nitrogen gas inlet 6...Nitrogen gas condensation end point 7 in heat exchanger 72...Liquid nitrogen outlet 9 in heat exchanger 72...Cold nitrogen gas population 10 in heat exchanger 50...
・Nitrogen gas outlet 12 in heat exchanger 50...Gas separation device (gas supply device) 14.16...Molecular sieve
18... Inlet conduit 20... Compression m 22... Outlet conduit 24.26, 28.30.32... Cock 34.
... Outlet conduit 36 ... Vacuum pump 38.40.42
... Cock 44 ... Supply conduit 48 ... Thermal insulation storage tank 50 ... Gas/gas heat exchanger (first heat exchanger) 51.
... Insulating material 52 ... Conduit 54 ... Cooling device 56 ... Heat exchanger 58 ... Conduit 60 ... Liquid trap (liquid separator) 62 ...
Liquid nitrogen 64... Gaseous nitrogen 65... Pressure balance conduit 66... Liquid nitrogen level 67... Float 68.
...Valve 70...Conduit 72...Liquid/? 1 gas heat exchanger (second heat exchanger) 7
4...Liquid nitrogen 76...T branch 78...Conduit
80... Pressure controller 82... Supply conduit 84...
Level controller 88...Valve element 90...Rondo 92...Support body 94...Valve seat 96...Hero 98...S IJ-F100...
・Nej; 102... Coil spring 104... Passage
106... Conduit 108... Storage container 112... Kotsuk 113...
...Reducing cock 114...Valve 115...Evaporator
116... Float 117... Conduit 118...
Liquid nitrogen level 120...Conduit A...Surface area of support 82 and valve element 88■...
Prestress po of the spring 102...Pressure pl in the storage tank 48...Opening pressure p2 going to the pressure controller 80...
User pressure (second pressure, service pressure) Δ11. ...
Subcooling enthalpy (achieved by heat exchanger 72) ΔIIC... Condensation enthalpy ΔH... Δ10 and Δl (sum of

Claims (1)

[Claims] 1. Supplying a gas at a first pressure greater than atmospheric pressure supplied by a gas supply device to a cooling device, and then subjecting the produced liquid to a second pressure equal to or lower than the first pressure. In order to liquefy the gas, the gas exiting the gas supply device is cooled by passing it through a first gas/gas heat exchanger before being supplied to the cooling device, and is then liquefied in the cooling device by condensation. The saturated liquid and moist vapor produced are led to a liquid separator, the saturated liquid discharged from the liquid separator and the moist vapor produced by expansion after the liquid separator already produced in a thermally insulated storage tank. The saturated liquid and the wet vapor are subcooled and condensed/subcooled in the second heat exchanger, respectively, and the subcooling level is transferred to the second heat exchanger. by means of a pressure controller connected to the cooling device, after which the second pressure is adjusted to a value corresponding to a maximum value of the second pressure equal to the pressure in the cooling device and a value equal to the pressure in the reservoir. a value corresponding to the minimum value of the second pressure, and evaporates a part of the liquid present in the thermally insulated storage tank using condensation heat and subcooling heat, thereby generating steam. The waste gas supplied by the gas supply device is guided to the first heat exchanger to cool it, and the liquid evaporated in the storage tank is replenished by a supply conduit connected downstream of the liquid separator. Gas liquefaction method. 2. The gas supply device is a known gas separation device, in which the pressure of the gas mixture at atmospheric pressure is increased by a compressor to a first pressure greater than atmospheric pressure, and then fed to a molecular sieve, 2. A method as claimed in claim 1, in which a gas fraction of a second type is passed through and a gas fraction of a second type is absorbed and desorbed, after which said gas fraction of a first type is supplied to said cooling device. 3. Liquefying the gas by supplying a gas at a first pressure greater than atmospheric pressure supplied by a gas supply device to a cooling device and then bringing the produced liquid to a second pressure equal to or lower than the first pressure. In the gas liquefaction apparatus, the outlet of the gas supply device is connected to a thermally insulated first heat exchanger, and the first heat exchanger is located in a thermally insulated storage tank together with a second heat exchanger and a liquid separator. and connected to a cooling device, the cooling device being disposed outside the thermally insulated storage tank, a liquid conduit of the cooling device being connected to the liquid separator, the liquid separator having an outlet conduit, and the liquid separator having an outlet conduit; An outlet conduit is connected to the second heat exchanger and to the user via a pressure controller, the opening pressure of the pressure controller being independent of the user pressure, and further connected to the thermally insulating container. Gas liquefaction device, characterized in that a level controller is provided, said level controller being connected to an outlet conduit of said liquid separator. 4. The second heat exchanger is also coupled to the level controller, the level controller comprising a valve that opens at a predetermined level of liquid in the reservoir to direct the liquid to the second heat exchanger.
4. The device of claim 3, wherein the thermally insulated reservoir can be supplied from a heat exchanger. 5. Apparatus according to claim 3, wherein the liquid separator is in the form of a known liquid trap. 6. The gas supply device is a known gas separation device comprising at least two molecular sieves for separating the desired type of gas from the gas mixture supplied to the gas supply device. The device according to paragraph 3.